Bug 1885366 - Add BackupResource to the backups source docs. r=backup-reviewers,kpatenio

Differential Revision: https://phabricator.services.mozilla.com/D204824

browser/components/backup/docs/backup-resources.rst

@@ -0,0 +1,18 @@
+================================
+Backup Resources Reference
+================================
+
+A ``BackupResource`` is the base class used to represent a group of data within
+a user profile that is logical to backup together. For example, the
+``PlacesBackupResource`` represents both the ``places.sqlite`` SQLite database,
+as well as the ``favicons.sqlite`` database. The ``AddonsBackupResource``
+represents not only the preferences for various addons, but also the XPI files
+that those addons are defined in.
+
+Each ``BackupResource`` subclass is registered for use by the
+``BackupService`` by adding it to the default set of exported classes in the
+``BackupResources`` module in ``BackupResources.sys.mjs``.
+
+.. js:autoclass:: BackupResource
+  :members:
+  :private-members:

browser/components/backup/docs/index.rst

@@ -11,3 +11,4 @@ into a single file that can be easily restored from.
    :maxdepth: 3
 
    backup-service
+   backup-resources

docs/conf.py

@@ -55,6 +55,7 @@ extensions = [
 # excluded from valid-jsdoc in the top-level .eslintrc.js.
 js_source_path = [
     "../browser/components/backup",
+    "../browser/components/backup/resources",
     "../browser/components/extensions",
     "../browser/components/migration",
     "../browser/components/migration/content",